Load responsive brake



Sept. 19, 1950 w. s. RANSOM 2,523,057

LOAD RESPONSIVE BRAKE? Filed Aug. v15, 1946 f s Sheets-Sheet 1 INVENTOR Willard G Farrsom.

MMIM

ATTO RN EYS Sept. 19, 1950 w. G. RANSOM LOAD RESPONSIVE BRAKE I5 Sheets-Sheet 2 Filed Aug. 15, 1946 MN 8 h NM 0 Q Q\ o N t N & 5 \v\\\\ om M Q 2 I N 2 Q mm Q [I Q Mm mm 1| W m h R 3 N- QM N *1 w a k R N w; h v H @1. N M Q A L R N b o INVENTOR m s m m a N R. R O m OY N w% Patented Sept. 19, 1950 LOAD RESPONSIVE BRAKE Willard G. Ransom, Homewood, Kans.

Application August 15, 1946, Serial No. 690,693

. This invention relates to brakes for vehicles which carry heavy loads such as motor trucks,

present braking apparatus, variable loading on vthe respectivewheels or shifting of the load from one wheel to another clue to momentum or centrifugal force results in unequal effective retardation of p the respective wheels. Thus, when the brakes are applied the less heavily loaded wheels are apt to skid and cause very serious accidents unless the brakes are skillfully applied by anexperienced operator. This hazard of skidding is especially aggravated when making an emergency application of the brakes.

The principal object of the present invention is, therefore, to provide a brake apparatus wherewith the braking forces effective on the respective. wheels are directly proportional to the load carried or acting thereon.

In accomplishing this and other objects of the invention hereinafter pointed out, I have provided improved structure, the preferred form 3 Claims. (Cl. 188-195) of which'is illustrated in the accompanying drawings wherein:

Fig. 1 is a perspective view ofthe rear portion of a vehicle chassis, particularly of a, truck, equipped with a brake apparatus embodying the features of the present invention.

Fig. 2 is a vertical section through the Wheels at one side of the chassis. Fig. 3 is a side elevational view of the vehicle rear frame, axle mounting spring and brake appara tus, the section being taken through the brake drum, and showing the brakes in released posisuch as the chassis of a motor truck having a 7 frame 2 supported at the front and rear ends by wheeled units as in standard truck design.

Therear unit 3 is illustrated as comprising an axle housing 4 secured to the frame 2 by elliptical type leaf springs 5 and 6, the axle being secured to the mid portion of the springs by spring seats I. The front ends of the springs are pivotally connected to brackets 8 carried by the sides of the frame 2 and the rear ends are connected with brackets 9 by shackles l0 and bell crank levers hereinafter described.

Journalled on the respective ends of the axle housing are wheels ll carried by hubs 12. The hubs I2 carry brake drums l3 cooperating with sets of brake shoes it and iii in applying a re-' tarding force on the wheels when the operator desires to retard speed of the vehicle or bring the vehicle to a stop. The brake shoes are illustrated of arcuate shape and have adjacent ends pivotally mounted as indicated at it and I! on backing plates or disks [8 that are carried on the axle housing and close the open sides of the brake drums 13. The opposite ends of the brake shoes are moved apart to bring the frictional surfaces "i9 thereof into contact with the braking surface 20 of the drums It by cam levers 2| fixed ,to shafts 22 journalled in the disks I8 and which have oppositely directed cam portions 23 and 24 engaging rollers 25 and 26 carried by the brake shoes of the respective sets. Turnin of the cam levers 2i in a clockwise direction (Fig.

3) moves the shoes I4 and I5 into contact with the drums l3 and the shoes are released upon reverse movement of the cam levers 2! under action of springs 21.

The shafts 22 are actuated by arms 28 that are actuated through individual power mechanisms designated 29 activated from a master control unit (not shown) by the operator of the truck. In the illustrated instance the power units include cylinders 36 substantially horizontally disposed alongside the frame and have ears 3! projecting from their ends which pivotally connect by pins 32 with brackets 33 that extend laterally from the vehicle frame 2 to align Slid of the cylinders 30 that face the levers 28 and" which have yok'es 31 on the free ends. The yokes 31 are connected with thebrake arms 28 by pins 38 extending through one of a series of apertures 39 in the ends of the respective brake arms 28. The brake actuating fluid isadmitted to the respective cylinders through ducts 413 leading brakes for the reason that under light loads the. force retarding rotation of the wheels is too great in proportion to the wheel traction on. the.

roadway.

Another difficulty is brought about through shifting of load from the wheels at one sideof.

the vehicle to the wheels at the other side under centrifugal force as when the vehicle is traveling on a curve, or through shifting of load from the rear'axle to the frontaxle under momentum as whenmaking an emergency stop. This momentary shifting. in loadon the. respective. wheels oftenresults in skidding of the temporarily less heavily loaded wheels at. the time the brakes are applied and may result in a, .seriousaccident.

In order to overcome these difiiculties,.1 pro.- vide each braking unit with, means for: controlling and restricting automatically the retarding. force in direct proportion to the load carried onv the respective wheels so that regardless of, different andvariable effective loads on the wheels.

the ultimate maximum effective. retardation, for

the wheels is kept substantially uniform and at. a rate to bring the vehicle quickly andsafely under control or to a stop.

In carrying out the invention, the disks or. backing plates l8 are mounted on the axle housing 4 so that they will turn with the brake drums to a limited extent but rotation thereof is resisted in accordance with the load carriedupon the The disks l8. preferably respective wheels H. include sleeve-like bearings 4| journalled on the. axle between the adjacent spring seats I and stop collars 42 that are threaded onto thewheel housing as shown in Fig. 2. Connected. with each disk l8 through a hub is a disk 46 having an ear extending upwardly adjacent the truck. frame and which is pivotally connected by a pin. with a link 4'! having its opposite end pivotally :2

connected'by a pin tlll'with an arm Q9 of a bell crank lever 59-previously referredto, the bell,

crank levers being journalled on pins carried by the brackets 9: The other'arm 52of'each bell crank St is pivotally connected by'a pin 53 with the spring shackles It).

With the construction thus described; admission'ofpressure fluid to the respective cylinders Z-Beffects movement of the pistonss land rocking of theobrake arms 28 tocausethe cam ends23 and 24 ofthe levers 2! to move the brake shoes Mend lfi-into contact with the brakingsurfaces 2!] of thebrake drums 3 to eifect'retardatiorr'ofthe wheels Has when retarding speed of-the vehiclev or bringing the'vehicle-to a stop. Upon contact of the brakeshoes ld -and l5-with the drums I3, turning of the wheels H tends to rotate the. backing plates lnwhich carry the brake shoes l4 and: IE but since thebacking plates !8 areancho-red by. the links All to the arm 49 of the bell crank levers 5!]?and the other to. the springs .5 and E by thespringshackles ID, rotation ofthe backing plateslltis resisted,- une lcssthefriction between the brake shoesland the.

arms 52 of the bell cranklevers are. connected drum is sufiicient to effect lift of the load. When this occurs, the relative position of the cam portions 23 and 24 change with respect to the brake shoe rollers 25 and 26 to reduce the pressure of the cams 23 and 24 on the shoes l4 and 15, thereby preventing the retarding forces on the wheels from reaching a value at which skidding is apt to occur.

The above described action is readily understood, by inspection of Figs. 3 and .4 of the drawings. For example, assuming that the brakes are to be applied, the operator, through a master unit or control valve, causes a flow of pressure medium through the duct 40 to the cylinder 30 which moves. the piston 34 therein toward the right, shifting the brake arm 28 in a clockwise direction. In case of a full emergency application, the piston reaches the end of the cylinder as shown in Fig. 4 to effect a substantially fixed position of the pivotal connection 38 between the piston rod and arm 28: Duringthis movement the cam lever 2| :rotates in a clock-wise direction from the position shown in Fig. 3 to effect movement-of the brakeshoes l4 and 15 into contact with the drum [3. If thefrictional contact between the brake shoes l6 and I5 and drum I3 is sufiicient to rotate'the backing plate H], the connecting link ll effects rockingmovement of the bell crank in an-anti-clockwise direction to exert a downward prying action on thespring and an upward lifting action on the frame of the vehicle through the bell crank pivot 5 l.

During this movement, the brake shoes M and [5 advance a corresponding distance in a clockwise direction and the lifting of the frame'results in changing the angular position of the brake lever so that the camportions 23 and 24 of the levers 2| are backed'off from the rollers 25* anchorageor temporary fulcrum when the cylinder pressure is high and the brake-shoe friction force'lifts the load andithatthe'downward pressureofthe load on the bell-crank 5!] is the force-which determines the amount'of retardation.

From the-foregoingit' is obvious that I have provided a relatively simple brake system whereby the maximum braking forces that can be applied on the respective wheels are directly under.

control of an proportional" to the loadacting on such wheels, consequently, the retardation forces which are applied even on emergency application'cannot'cause skids when the vehicleis lightly loaded or-when' the loadshifts from one wheel to'anothenas' in case of stopping momentum or through the effects of centrifugal force while the truckis traveling ona curved.

roadway.

What. I claim and "desire to secure by Letters Patent is:

1i Ina-vehicle having a wheel-forsupporting a portion of aload to be carried-onthe vehicle,-

the power unit.

a brake drum for said wheel, brake shoes, means for supporting the brake shoes for contact with the drum and for turning movement relatively to the drum responsive to rotational pull of the 2. In a vehicle including an axle, wheels rotatably mounted at the ends of the axle, a vehicle frame, springs connecting the ends of the axle with the frame, a brake drum on each wheel, brake shoe carriers rotatable on the ends of the axle, brake shoes pivotally supported on the brake shoe carriers, .cam levers on the carriers for moving the brake shoes into and out of frictional contact with the brake drums, lever arms connected with the cam levers, powercylinders car-- 3. In a vehicle including an axle, a wheel rotatably mounted at an end ofthe axle, a vehicle frame, a spring connecting said end of the axle with said frame, a brake drum on said wheel, a brake shoe carrier rotatable on said end of the axle, shoes pivotally supported on the brake shoe carrier and adapted to engage said drum, a cam lever carried by the brake shoe carrier for moving the brake shoes into and out of frictional contact with the brake drum, an arm connected with the cam lever, a power cylinder carried by the frame,a piston slidable in the cylinder, means connecting the piston with said arm, means for lifting the load carried by the frame and acting on said wheel, and a link connecting said lifting means with the brake shoe carrier for lifting the load acting on the wheel to limit rotation of the ried by sides of the frame, pistons slidable in.

the cylinders, means connecting the pistons with said lever arms, lifting means connecting the springs with the frame for lifting the load aeting on the respective wheels, and links connecting said lifting means with the brake shoe carriers for lifting the load acting on the respective riers by the drums when the brake shoes are engaged with said brake drums.

wheels responsive to pull on the brake shoe earshoe carrier by pull of the drum when the brake shoes are engaged with said brake drum for modifying the power applied to the brake shoes.

WILLARD G. RANSOM.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number 7 Name Date 1,804,697 Lord May 12, 1931 2,250,725 Ransom July 29, 1941 FOREIGN PATENTS Number Country Date Great Britain July112, 1923 

